Composition and method of inhibiting corrosion of ferrous metals by aminestabilized chlorinated hydrocarbons



United States Patent COMPOSITION AND METHOD OF INHIBITING CORROSION F FERROUS METALS BY AMINE- STABILIZED CHLORINATED HYDROCARBQNS (USING POLYHYDROXY BENZENES) Wilbur H. Petering and William A. Callahan, Detroit, Mich., assignors to Detrex Chemical Industries, Inc, Detroit, Mich., a corporation of Michigan No Drawing. Original application July 23, 1954, Ser. No. 445,474. Divided and this application June 10, 1958, Ser. No. 741,003

20 Claims. (Cl. 252171) weights and are subject to decomposition by metals or oxygen, or in their presence, and this decomposition is accelerated by light and heat.

It is conventional in the art to add stabilizers of various types to chlorinated hydrocarbons. Among the accepted stabilizers are the phenolic compounds, aryl amines, and various azo compounds. However, the use of such compounds is quite limited except in the case of a few of the higher boiling chlorinated hydrocarbons, since the stabilizers also have relatively high boiling points. A wide difference in boiling points between the solvent and the stabilizer is undesirable becauseof the difiiculty of stabilizing the vapor phase, and it is desirable to provide a combination of solvent and stabilizer not having a wide difference in boiling points.

The organic amine bases have enjoyed widespread use as stabilizers for unsaturated chlorinated hydrocarbons. Such bases, including primary aliphatic amines having the NH radical and basic cyclic compounds characterized by nitrogen in the ring such as pyridine'and the like are disclosed in the patents to Dinley, Numbers 2,096,735, 2,096,736 and 2,096,737. Under many conditions the primary aliphatic and cyclic amine bases disclosed in the Dinley patents are highly effective and desirable stabilizers for chlorinated hydrocarbons.

In the manufacture of the unsaturated chlorinated hydrocarbons as trichlorethylene, for example, the recovery of a neutral, sweet, relatively pure product is almost impossible without the use of a stabilizer such as these amines. The amine stabilizer should be present in the refining operation, as distinguished from adding amine to the refined product, and the amine should be volatile with the chlorinated hydrocarbon and therefore carry over from the refining operation into the refined product. Unless a neutral, sweet product is obtained when the solvent is refined, subsequent attempts to stabilize the solvent often prove futile, or at least extremely costly and time consuming. Thus, the amines are not only highly effective and desirable stabilizers, but their use in both the liquid and vapor in the last stages of manufacture is almost essential.

Yet, in spite of the eifectiveness and desirability of the amines'as stabilizers, there appears to have been an undesirable reaction or set of reactions which take place when the amines are used as stabilizers in unsaturated chlorinated hydrocarbon solvents in the presence of certain metals of the iron group. It has now been discovered that the lower boiling unsaturated chlorinated hydrocarbons, when stabilized with certain of the conventional organic amines, such amines having boiling points which are not widely ditferent from the boiling point of the chlorinated hydrocarbon, appear to enter'into a complex reaction when exposed to oneof those metals; The reaction appears to be metal-induced, causing a progressive decomposition of the chlorinated hydrocarbons. The reaction which occurs in the presence of conventional amines causes attack on the metal, rapid loss of amine stabilizer and the development of acidic materials, and apparently the series of reactions producing the decomposition requires the presence of the amine.

The corrosive action ofthe amines appears to be related to certain'specific metals, especially iron (also in its common alloyed form as steel) and copper (alone or In referring to amines in the foregoing'paragraph,

we have used the term in its broad sense. The other organic bases specified in the Dinley patents, including cyclic compounds characterized by nitrogen in the ring, such as pyridine and morpholine, for example, are included within the meaning of this term. Among the suit able amines which are listed in the examples set forth hereinafter, and which are accordingly suitable in the practice of this invention are pyridine, di-sec butylamine, diisopropylamine, diethylamine, n butylamine, amylamine, methyl pyridine, n-methyl morpholine, triethylamine, and hexylamine.

The exact mechanism by which the amine reacts with the chlorinated hydrocarbon in the presence of the metal is not completely known or understood. It may be that the amine, being a strong base, that is, a Lewis base or electron donor, either forms a covalent bond with one carbon atom of the unsaturated chlorinated hydrocarbon, and the resulting fragment reacts with the metal, or, in the case of chlorinated hydrocarbons containing hydrogen, the amine may react by first removing a hydrogen to yield ionic fragments which in turn are reactive toward metals-the end products of such reactions being more or less complex metal-organic chloro compounds. Then again, the metal may be the initiator of the set of reactions which involve the amine and the chlorinated solvent.

One, explanation for the reaction is that the unsaturated chlorinated compound, being amphoteric, that is, having one carbon basic and the other acid at the unsaturated bond, and the amine being basic, that is, a Lewis base and an electron donor, forms a covalent-bond at the acidic carbon leaving the resultant fragment basic and that a metal brings about chelation. In any event, serious corrosion problems are encountered when a low-boiling unsaturated chlorinated hydrocarbon is stabilized with an amine and the product exposed to a fenrous metal, or copper, particularly when the hydrocarbon is a hot, bonedry liquid.

It is accordingly an object of this invention to provide a composition and method for overcoming the foregoing disadvantages. Still another object is' to provide an improved corrosion-resistant stabilizer composition for the lower boiling unsaturated chlorinated hydrocarbons. Other objects and advantages of this invention will further appear hereinafter.

In accordance with this invention, the corrosive action of the organic amine in the presence of metals in the chlorinated hydrocarbon is overcome by incorporating into the mixture a small amount of a polyhydroxy benzene which interferes with the corrosive action of the amine in the presence of ferrous metals. The polyhydroxy benzene does not interfere with the stabilizing action of the amine, or its ability to act as an alkaline material or to act as a reducing agent. These polyhydroxy benzenes are characterized by the fact that they have two hydroxyl groups in meta positions to each other. It appears that these polyhydroxy benzenes act to retard or interfere with the corrosive activity of the amine by either hindering the amine itself, or by forming a protective layer over the surface of the metal. In the former case the amount of polyhydroxy benzene required to control the action of the amine is related to the amount of amine used, while in the latter case the amount of polyhydroxy benzene required is related to the surface area of the metal exposed to the solvent and amine.

It has been found that in a few cases, if the amine, when used in the usual stabilizing concentration, reacts oration, is combined with a stabilizing proportion of amine. The stabilized product is combined with an inhibitive proportion of a polyhydroxy benzene selected from the group consisting'of the compounds listed above and their equivalent compounds. The resulting mixture is heated in a still, which volatilizes the amine and chlorinated hydrocarbon but not the polyhydroxy benzene. Since the severe corrosion problem occurs in the substantially anhydrous liquid phase, the polyhydroxy benzene is retained at the location where it is most needed. At the sam time, the amine stabilizes the chlorinated hydrocarbon in the liquid and vapor phases.

Unsaturated chlorinated hydrocarbons such as trichlorethylene and perchlorethylene are widely used as degreasing solvents, cleanersand the like. For example, ferrous metals are degreased commercially by subjecting them to liquid and to vapor phase chlorinated hydrocarbons. Since the liquid hydrocarbon is heated and contains amine, and since it is anhydrous and in the liquid phase, there is some danger of corrosion of the degreesing apparatus or of the metal immersed in the liquid. Accordingly, it is commercially advantageous to provide a chlorinated hydrocarbon solvent which contains both an amine and, a polyhydroxy benzene in accordance with this invention.

with the chlorinated solvent and the metal exposed to the stabilizer and solvent, the activity can be reduced by using a greatly increased concentration of stabilizer as, for example, about ten times the usual stabilizing amount. It is believed that the very large amount of aminestabilizer is able to form a-protective coating over the metal surface, thus interfering in the reaction between the amine, solvent and metal. That method of controlling the activity of amine is not desirable because such large amounts of'amine add to the cost of stabilizing the solvent; moreover, if under some condition the concentration of amine should become depleted, the concentration would fall into that level Where the reactivity of the amine would rapidly increase and the corrosion difificulties mentioned above would be encountered.

This invention includes the polyhydroxy benzenes wherein at least two hydroxy groups are meta to each other. Such compounds are represented by the generic formula and the following specific compounds are illustrative:

(1) Resorcinol (2) Pyrogallol (3) Phlorglucinol (4) Methyl pyrogallol (1, 3, 4, 5) (5) Hydroxy hydroquinone (6) 2 methyl resorcinol (7) 4 methyl resorcinol (8) 4,5 dimethyl resorcinol In accordance-with this invention, the crude unsaturated chlorinated hydrocarbon, prior to the refining op- It is well known that the proportions of amine stabilizers may vary from trace values (such as .Ol% by weight or less) to as high as 1.0% by weight, based on the weight of the chlorinated hydrocarbon. However, a range of the order of about .02.20% by weight repre sents the proportions considered commercially preferable in most amine-stabilized chlorinated hydrocarbons. Amine stabilizers have been well known and extensively used, and different amines have been used indifferent proportions for different chlorinated hydrocarbons. The art is well awareof the proper proportions of each spe- .c'ific amine stabilizer in each specific chlorinated hydrocarbon, and such proportions are conventionally referred to as stabilizing proportions, and are so defined here- The proportions of the polyhydroxy benzene may be varied from about .0l% by weight to about 5% by weight, but a range of about .01-.15% by weight is preferred. Such proportions are referred to as inhibitive proportions, and are so defined herein. Preferably, the weight of polyhydroxy benzene is about l-5 times the weight of amine stabilizer. The eifect of these polyhydroxy benzenes is shown in the results of tests described below:

A chlorinated hydrocarbon is refluxed in the presence of a weighed piece of metal. A stabilizing amount of an amine is added and the solvent refluxed continuously. After refluxing for at least 48 hours the solvent is titrated for alkalinity and the metal weighed to determine the loss of metal. Similar tests, in which an inhibiting amount ofpolyhydroxy benzene has been added along with the amine, are him. Also tests, in which the polyhydroxy benzene is used alone without amine, are run.

The foregoing reflux test has been used in industry to evaluate chlorinated solvents for use in such processes as degreasing. Since the test is not particularly severe it does not evaluate stability of the solvent or the eificacy of the stabilizer used. Therefore in the absence of a stabilizer or in the presence of a weak stabilizer, the breakdown of the solvent is not particularly rapid. Therefore, because the test duplicates a continuous refluxing condition which would exist under normal conditions of use, it serves as a valuable tool in showing the reaction of the amine and solvent in the presence of metal.

The results of numerous such tests are shown in Tables IA and IB.

. L Mn TABLE IA Inhibitory Efiect on Steel of Polyhydroxy Benzenes m Trzchlorethylene Amine, Polyhydroxy Hours Loss 01' Loss of Amine percent Cpd. ded, of Alkalinity Metal,

by weight percent by weight Test ppm. Hdl MgmJFt.

Refined Pyridine 02 None 134. 5 272.0 1, 917 D ..02 .01% Pyrogallol- 134. 41. 5 77 .20 None 134. 5 939. 0 10, 800 20 .Ol% Pyrogallo 134. 5 244.0 77 02 None 134. 5 113.0 +34 02 .01% Pyrogallol- 134. 5 141. 0 5 20 None 134. 5 5. 6 +19 .20 .Ol% Pyrogallol. 134. 5 3. 4 9 .02 None 165.0 31.5 110 .02 01% Pyrogallol..- 165. 0 7. 2 62 20 None 165. 0 250. 0 72 20 .01% Pyrogallol- 165. 0 612. O 29 02 None 132. 0 520. 0 1, 509 .02 01% Pyrogallo 132. 0 120.0 24 02 None 132. 0 875.0 1, 355 02 .017 Pyrogallol. 132. 0 480. 0 202 .20 None 132.0 1, 470. 0 5, 700 20 .01% Pyrogallol- 132. 0 328. 0 648 02 None 165. 0 228.0 1, 110 20 -do 165. 0 1, 060.0 8, 100 I .20 .0 l% Pyrogallol. 165. 0 940. 0 5,530 0 -do 165. 0 0. 0

TABLE IB Inhibitory Effect on Steel 0 Polyhydroxy Benzenes m Perchlorethylene Amine; Polyhydroxy Hours Loss of Loss of Amine percent Benzene added, of Alkalinity Metal,

by weight percent by weight Test p.p.m. Hdl MgmJFt.

Hexylamine 02 None 136 86. 4 274 Do. .02 .Ol% Pyrogallol. 136 36. 0 163 Do .20 None 136 250.0 570 -Do 7 .0l% Pyrogallol... 136 134. 0 ,508 Disec. Butylamine. .02 None 63 75. 2 l, 208 o. .02 .01% Pyrogallo 63 7. 2 129 Refined Morpholin 02 None 120 54. 0 253 Do 02 .01% PyrogalloL 120 258. 0 70 Morpholine. 02 None 63 87. 7 1, 185 02 .01% Pyroga-llol--- 63 2. 2 157 20 None 120 295. 0 605 20 01% PyrogalloL 120 80. 5 270 02 None 120 59. 4 122 02 .01% Pyrogallol. 120 45. 0 20 None 120 230. 0 348 120 137.0 4 87 5. 6 +37 The beneficial efiects observed in Tables IA and IB were not the result of a stabilizing property of the polyhydroxy benzene itself. Several anti-oxidants or stabilizers which are known in the art and accepted as efiective inhibitors were added to the chlorinated solvent along with an amine. No inhibitory effects on the action of the amine were observed. If anything, the activity of the amine was increased, as indicated by the fact that attack on the metal was initiated somewhat sooner than when the amine is present alone. Also, in a number of cases, the tests were discontinued while the solvent was still alkaline and in spite of this fact, considerable attack on the metal had already taken place. This indicates that the corrosive action on the metal is not the result of a lack of stabilizer or the action of an unstable solvent.

Having thus described our invention, we claim:

1. A stabilized solvent which is substantially noncorrosive to ferrous metals consisting essentially of a volatile low-boiling low molecular weight unsaturated chlorinated hydrocarbon which is normally subject to decomposition by metals and oxygen containing an organic amine selected from the group consisting of pyridine, di sec. butylamine, diisopropylamine, diethylamine, nbutylarnine, amylamine, methylpyridine, N-methyl morpholine, triethylamine, and hexylamine, and having a boiling point near that of the chlorinated hydrocarbon in a stabilizing proportion in an amount of from about .01% to about 1.0% by weight of said solvent, said amine stabilized solvent in the presence of ferrous metals causing metal corrosion, in combination with an inhibitor for said ferrous metalamine corrosion comprising a polyhydroxy benzene wherein at least two hydroxy groups are in the meta position relative to each other, said corrosion inhibitor being present in an amount from about .0l%-5% by weight.

2. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is resorcinol.

3. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is pyrogallol.

4. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is phlorglucinol.

5. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is methyl pyrogallol (1,3,4,5).

6. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is hydroxy hydroquinone.

7. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is 2 methyl resorcinol.

8. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is 4 methyl resorcinol.

9. The stabilized solvent defined in claim 1 wherein the polyhydroxy benzene is 4,5 dimethyl resorcinol.

10. In a process wherein a volatile unsaturated low molecular weight chlorinated hydrocarbon is exposed in the hot anhydrous liquid state to a ferrous metal, said hydrocarbon including a stabilizing proportion of an organic amine selected from the group consisting of pyridine, di sec. butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, N-methyl morpholine, triethylamine, and hexylamine, in the amount of from about .01% to about 1.0% by weight of said solvent which normally reacts with the chlorinated hydrocarbon and ferrous metal in the presence of said metal to corrode said metal, the improvement which comprises incorporating into the said chlorinated hydrocarbon and amine about .01% by weight of an inhibitor for said ferrous metal-amine corrosion comprising a polyhydroxy benzene wherein at least two hydroxy groups'are in the meta position relative to each other.

11. The process defined in claim wherein the polyhydroxy benzene is resorcinol. V

12. The process defined in claim 10 wherein the polyhydroxy benzene is pyrogallol.

13. The process defined in claim 10 wherein the polyhydroxy benzene is phlorglucinol.

14. The process defined in claim 10 wherein the polyhydroxy benzene is methyl pyrogallol (1,3,4,5).

15. The process defined in claim 10 wherein the poly I hydroxy benzene is hydroxy hydroquinone.

16. The process defined in claim 10 wherein the polyhydroxy benzene is 2 methyl resorcinol.

17. The process defined in claim 10 wherein the polyhydroxy benzene is 4 methyl resorcinol.

18. The process defined in claim 10 wherein the polyhydroxy benzene is 4,5 dimethyl resorcinol.

19. A stabilized solvent which is substantially noncorrosive to ferrous metals consisting essentially of a volatile low-boiling low molecular weight unsaturated chlorinated hydrocarbon which is normally subject to decomposition by metals and oxygen, containing as a stabilizer about .01% to .20% of an organic amine selected from the group consisting of pyridine, di sec. butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, N-methyl morpholine, triethylamine, and hexylamine, and having a boiling point near that of the chlorinated hydrocarbon, said amine 0 stabilized solvent in the presence of ferrous metals causing metal corrosion, in combination with an inhibitor for said ferrous metal-amine corrosion comprising a polyhydroxy benzene wherein at least two hydroxy groups are in the meta position relative to each other, said corrosion inhibitor being present in an amount from about .01%5% by weight.

20. In a process wherein a volatile unsaturated low molecular weight chlorinated hydrocarbon is exposed in the hot anhydrous liquid state vto a ferrous metal, said hydrocarbon including as a stabilizer about .01%-.20% by weight of anorganic amine selected from the group consisting of pyridine, di sec. butylamine, diisopropylamine, diethylamine, n-butylamine, amylamine, methyl pyridine, N-methyl morpholine, triethylamine, and hexylamine which normally reacts with the chlorinated hydrocarbon and ferrous metal in the presence of said metal to corrode said metal, the improvement which comprises incorporating into the said chlorinated hydrocarbon and amine about .01 %-5%. by weight of an inhibitor for said ferrous metal-amine corrosion comprising a polyhydroxy benzene wherein atleast two hydroxy groups are in the meta position relative to each other.

Great Britain Sept. 4, 1933 

1. A STABILIZED SOLVENT WHICH IS SUBSTANTIALLY NONCORROSIVE TO FERROUS METALS CONSISTING ESSENTIALLY OF A VOLATILE LOW-BOILING LOW MOLECULAR WEIGHT UNSATURATED CHLORINATED HYDROCARBON WHICH IS NORMALLY SUBJECTED TO DECOMPOSITION BY METALS AND OXYGEN CONTAINING AN ORGANIC AMINE SELECTED FROM THE GROUP CONSISTING OF PYRIDINE, DI SEC. BUTYLAMINE, DIISOPROPYLAMINE, DIETHYLAMINE, NBUTYLAMINE, AMYLAMINE, METHYLPYRIDINE, N-METHYL MORPHOLINE, TRIETHYLAMINE, AND HEXYLAMINE, AND HAVING A BOILING POINT NEAR THAT OF THE CHLORINATED HYDROCARBON IN A STABILIZING PROPORTION IN AN AMOUNT OF FROM ABOUT .01% TO ABOUT 1.0% BY WEIGHT OF SAID SOLVENT, SAID AMINE STABILIZED SOLVENT IN THE PRESENCE OF FERROUS METALS CAUSING METAL CORROSION, IN COMBINATION WITH AN INHIBITOR FOR SAID FERROUS METALAMINE CORROSION COMPRISING A POLYHYDROXY BENZENE WHEREIN AT LEAST TWO HYDROXY GROUPS ARE IN THE META POSITION RELATIVE TO EACH OTHER, SAID CORROSION INHIBITOR BEING PRESENT IN AN AMOUNT FROM ABOUT .01%-5% BY WEIGHT. 